Kep1er is a K-Pop girl group from South Korea, formed through the 2021 survival competition TV show Girls Planet 999. The group was put together by South Korean entertainment and mass media company CJ E&M, and is made up of nine members: leader Choi Yu-jin, co-leader Mashiro Sakamoto, Kim Chae-hyun, Huening Bahiyyih, Kim Da-yeon, Seo Young-eun, Kang Ye-seo, Hikaru Ezaki, and Shen Xiaoting. The group was spawned from the Girl Planet 999 competition series, which aired from August 6 to October 22, 2021. The show had the participation of 99 contestants from China, Japan, and South Korea. Several of the final 9 were already active in the entertainment business, such as eventual leader Choi Yu-jin, who was already part of the girl group CLC. Once formed as Kep1er (the name deriving from Johannes Kepler and his laws of planetary motion), the group made their debut with the single “Wa Da Da,” which hit the Billboard Global 200 chart at number 117, as well as number 16 in Japan, number 11 in Singapore, and number 13 in the US World Digital Songs Chart. “Wa Da Da” was followed by the group’s debut EP, titled First Impact, which hit number 1 on the Gaon Albums Chart. The group's winning streak continued in the following years thanks to commercially successful releases such as the EPs Doublast (2022), Troubleshooter (2022), Lovestruck! (2023), and Magic Hour (2023), all of which managed to crack the Top 5 of the South Korean charts. In 2024, Kep1er released their first Japanese LP Kep1going, which also served as the group's studio debut. The 15-track album climbed to number 3 on the Oricon charts and number 2 on the Japanese Hot 100, selling approximately 116,000 copies on its release date. On May 13, Kep1er announced the release of their debut Korean studio album Kep1going On, which was released on June 3. Later, discussions about extending Kep1er's contract beyond its initial duration of two years and six months began in September 2023 as the group faced potential disbandment by mid-2024. By January 2024, these discussions were ongoing, with the group's contract set to expire in July. However, by May 30, WakeOne confirmed that all members except Mashiro and Yeseo had renewed their contracts, leading to Mashiro and Yeseo's departure after the concert in Yokohama on July 15. On September 30, 2024, Kep1er signed with Klap Entertainment for co-management with WakeOne and announced their sixth EP Tipi-tap, which was released on November 1 as their first project with the now seven-member group. Their first Japanese EP, AGAINST THE WORLD, was released on April 30, 2025. On March 31, 2026 Kep1er released their 8th EP, CRACK CODE.
